Devices and methods using an expandable body with internal restraint for compressing cancellous bone

ABSTRACT

Devices and methods compress cancellous bone. In one arrangement, the devices and methods make use of an expandable body that includes an internal restraint coupled to the body. The internal restraint directs expansion of the body. In one arrangement, a method for treating bone inserts the device having the internal restraint inside bone and causes directed expansion of the body in cancellous bone. Cancellous bone is compacted by the directed expansion.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of co-pending application Ser.No. 10/044,843, filed Jan. 11, 2002, which is a divisional ofapplication Ser. No. 10/054,736, filed Oct. 24, 2001, now abandoned, andwhich is also a continuation-in-part of application Ser. No. 09/754,451,filed Jan. 4, 2001, which is a continuation of application Ser. No.08/871,114, filed Jun. 9, 1997, now U.S. Pat. No. 6,248,110, which is acontinuation-in-part of application Ser. No. 08/659,678, filed Jun. 5,1996, now U.S. Pat. No. 5,827,289, which is a continuation-in-part ofapplication Ser. No. 08/485,394, filed Jun. 7, 1995, now abandoned,which is a continuation-in-part of application Ser. No. 08/188,224,filed Jan. 26, 1994, now abandoned.

FIELD OF THE INVENTION

[0002] This invention relates to the treatment of bone conditions inhuman and other animals.

BACKGROUND OF THE INVENTION

[0003] When cancellous bone becomes diseased, for example, because ofosteoporosis, avascular necrosis, or cancer, the surrounding corticalbone becomes more prone to compression fracture or collapse. This is atleast in part because the cancellous bone no longer provides interiorsupport for the surrounding cortical bone. The bone disease may alsoaffect the strength and integrity of the surrounding cortical bone,further disposing the bone to fracture and/or collapse.

[0004] There are 2 million fractures each year in the United States, ofwhich about 1.3 million are caused by osteoporosis alone. There are alsoother bone diseases involving infected bone, poorly healing bone, orbone fractured by severe trauma. Moreover, the use of various drugs,such as steroids, tobacco and/or the excessive intake of alcohol, cansignificantly degrade bone quality. Any of these conditions, if notsuccessfully addressed, can result in fracture and/or collapse of bone,causing deformities, chronic complications, and an overall adverseimpact upon the quality of life.

[0005] U.S. Pat. Nos. 4,969,888 and 5,108,404 disclose apparatus andmethods for the fixation of fractures or other conditions of human andother animal bone systems, both osteoporotic and non-osteoporotic. Amongother inventions, these patents disclose devices and methods that employan expandable body to compress cancellous bone and/or create an interiorcavity within the targeted bone. The cavity receives a filling material,which hardens and provides renewed interior structural support forcortical bone.

[0006] The better and more efficacious treatment of bone disease thatthese patents promise can be more fully realized with improved systemsand methods for making and deploying expandable bodies in bone.

SUMMARY OF THE INVENTION

[0007] One aspect of the invention provides devices and methods forcompressing cancellous bone. In one arrangement, the devices and methodsmake use of an expandable body that includes an internal restraintcoupled to the body. The internal restraint directs expansion of thebody. In one arrangement, a method for treating bone inserts the devicehaving the internal restraint inside bone and causes directed expansionof the body in cancellous bone. Cancellous bone is compacted by thedirected expansion.

[0008] Another aspect of the invention provides devices and methods forcompacting cancellous bone. In one arrangement, the devices and methodsmake use of a body adapted to be inserted into bone and undergoexpansion in cancellous bone to compact cancellous bone. The bodyincludes material that, during the expansion in cancellous bone, appliesa force capable of moving fractured cortical bone, and further includesan interior membrane to constrain the expansion in cancellous bone. Inone arrangement, a method for treating bone inserts the device havingthe internal membrane inside bone and causes restrained expansion of thebody in cancellous bone. Cancellous bone is compacted by the restrainedexpansion.

[0009] Features and advantages of the invention are set forth in thefollowing Description and Drawings, as well as in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a perspective view of a first embodiment of a balloonconstructed in accordance with the teachings of the present invention,the embodiment being in the shape of a stacked doughnut assembly;

[0011]FIG. 2 is a vertical section through the balloon of FIG. 1 showingthe way in which the doughnut portions of the balloon of FIG. 1 fit intoa cavity of a vertebral body;

[0012]FIG. 3 is a schematic view of another embodiment of the balloon ofthe present invention showing three stacked balloons and string-likerestraints for limiting the expansion of the balloon in variousdirections of inflation;

[0013]FIG. 4 is a top plan view of a spherical balloon having acylindrical ring surrounding the balloon;

[0014]FIG. 5 is a vertical section through the spherical balloon andring of FIG. 4;

[0015]FIG. 6 shows an oblong-shaped balloon with a catheter extendinginto the central portion of the balloon;

[0016]FIG. 6A is a perspective view of one way in which a catheter canbe arranged relative to the inner tubes for inflating the balloon ofFIG. 6;

[0017]FIG. 7 is a suction tube and a contrast injection tube forcarrying out the inflation of the balloon and removal of debris causedby expansion from the balloon itself;

[0018]FIG. 8 is a vertical section through a balloon after it has beendeflated and as it is being inserted into the vertebral body of a human;

[0019]FIGS. 9, 9A, and 9B are side elevational view of a cannula showinghow the protective sleeve or guard member can expand when leaving thecannula;

[0020]FIG. 10 is a perspective view of another embodiment of a balloonof the present invention formed in the shape of a kidney bean;

[0021]FIG. 11 is a perspective view of the vertebral bone showing thekidney shaped balloon of FIG. 10 inserted in the bone and expanded;

[0022]FIG. 12 is a top view of a kidney shaped balloon formed of severalcompartments by a heating element or branding tool;

[0023]FIG. 13 is a cross-sectional view taken along line 13-13 of FIG.12 but with two kidney shaped balloons that have been stacked;

[0024]FIG. 14 is a view similar to FIG. 11 but showing the stackedkidney shaped balloon of FIG. 13 in the vertebral bone;

[0025]FIG. 15 is a top view of a kidney balloon showing outer tuftsholding inner strings in place interconnecting the top and bottom wallsof the balloon;

[0026]FIG. 16 is a cross-sectional view taken along line 16-16 of FIG.15;

[0027]FIG. 17A is a dorsal view of a humpback banana balloon in a rightdistal radius;

[0028]FIG. 17B is a cross-sectional view of FIG. 17A taken along line17B-17B of FIG. 17A;

[0029]FIG. 18 is a spherical balloon with a base in a proximal humerusviewed from the front (anterior) of the left proximal humerus;

[0030]FIG. 19A is the front (anterior) view of the proximal tibia withthe elliptical cylinder balloon introduced beneath the medial tibialplateau;

[0031]FIG. 19B is a three-quarter view of the balloon of FIG. 19A;

[0032]FIG. 19C is a side elevational view of the balloon of FIG. 19A;

[0033]FIG. 19D is a top plan view of the balloon of FIG. 19A;

[0034]FIG. 20 is a spherically shaped balloon for treating avascularnecrosis of the head of the femur (or humerus) as seen from the front(anterior) of the left hip;

[0035]FIG. 20A is a side view of a hemispherically shaped balloon fortreating avascular necrosis of the head of the femur (or humerus);

[0036]FIG. 21 is a balloon for preventing and/or treating hip fractureas seen from the anterior (front) of the left hip;

[0037] FIGS. 22A-C are schematic illustrations of a representativemethod and system for delivering a therapeutic substance to a boneaccording to the present invention; and

[0038]FIG. 23 is another embodiment of an expandable structureincorporating an internal expansion restraint;

[0039] FIGS. 24A-C are cross-sectional views of the expandable structureof FIG. 23 undergoing expansion in air;

[0040]FIG. 25A is a front view of another embodiment of an expandablestructure for use in compressing cancellous bone and/or displacingcortical bone;

[0041]FIG. 25B is a side view of the structure of FIG. 25A;

[0042]FIG. 25C is a perspective view of the structure of FIG. 25A; and

[0043]FIG. 26A is side view of a cavity forming device carrying anexpandable structure of the type shown in FIGS. 23 and 24A to 24C;

[0044]FIG. 26B is a perspective view of the distal end of the cavityforming device shown in FIG. 26A, showing the assembly of the proximalend of the expandable structure to the distal end of the outer catheterbody of the device;

[0045]FIG. 26C is a perspective view of the distal end of the cavityforming device shown in FIG. 26A, after the proximal and distal ends ofthe expandable structure have been secured, respectively, to the distalend of the outer catheter body and the distal end of the inner catheterbody of the device;

[0046]FIG. 27 is another embodiment of an expandable structure; and

[0047]FIG. 28 is a side view of the distal tip of a cavity-formingdevice.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0048] I. Balloons for Anatomical Structures

[0049] The present invention is directed to a balloon that can be usedto treat bones predisposed to fracture or collapse. These balloonscomprise one or more inflatable balloon bodies for insertion into saidbone. The body has a preferred shape and size when substantiallyinflated sufficient to compress at least a portion of the innercancellous bone to create a cavity in the cancellous bone and/or torestore the original position of the outer cortical bone, if fracturedor collapsed. In various embodiments, the balloon body is restrained tocreate said preferred shape and size so that the fully inflated balloonbody is desirably inhibited from applying substantial pressure to asingle point on the inner surface of the outer cortical bone if saidbone is unfractured or uncollapsed.

[0050] In addition to the shape of the inflatable device itself, anotherimportant aspect is the construction of the wall or walls of the balloonsuch that the proper inflation of the balloon body is achieved toprovide for optimum compression of the cancellous bone. The material ofthe balloon is also desirably chosen so the balloon can be insertedquickly and easily into a bone through a cannula, yet can also withstandhigh pressures when inflated. For example, the material could be chosento facilitate folding of the balloon. Alternatively, the material coulddesirably allow plastic, elastic and/or semi-elastic deformation of theballoon during inflation. The material will also desirably resistabrasion and/or puncture of the balloon when in contact with corticaland/or cancellous bone during introduction and inflation of the balloon.The balloon can also include optional ridges or indentations which areimparted to the cavity, desirably remaining in the cavity walls afterthe balloon has been removed, to enhance the stability of the bone voidfiller. Also, the inflatable device can be made to have an optional,built-in suction catheter. This may be used to remove any fat or fluidextruded from the bone during balloon inflation in the bone. Also, theballoon body can be protected from puncture (by the surrounding bone orcannula) by being covered while inside the cannula and/or bone with anoptional protective sleeve of suitable materials, such as Kevlar® fiberproducts or polyethylene tetraphthalate (PET) or other polymer orsubstance that can protect the balloon. This covering material may alsoprovide the additional advantage of reducing friction between theballoon and cannula, or it can incorporate a lubricating material, suchas silicone, to reduce friction. One important purpose of the inflatabledevice, therefore, is the forming or enlarging of a cavity or passage ina bone, especially in, but not limited to, vertebral bodies.

[0051] In one aspect, the invention provides an improved balloon-likeinflatable device for use in carrying out a surgical protocol of cavityformation in bones to enhance the efficiency of the protocol, tominimize the time required to performing the surgery for which theprotocol is designed, and to improve the clinical outcome. If desired,these balloons may approximate the inner shape of the bone they areinside of in order to maximally compress cancellous bone. They may alsohave additional design elements to achieve specific clinical goals. Invarious embodiments, they are made of inelastic, semi-elastic,elastomeric or plastically deformable materials and kept in theirdefined configurations when inflated, by various restraints, including,but not limited to, use of inelastic, semi-elastic, elastomeric orplastically deformable materials in conjunction with the balloon body,seams in the balloon body created by bonding or fusing separate piecesof material together, or by fusing or bonding together opposing sides ofthe balloon body, woven material bonded inside or outside the balloonbody, strings or bands placed at selected points in the balloon body,and stacking balloons of similar or different sizes or shapes on top ofeach other by gluing or by heat fusing them together. Optional ridges orindentations created by the foregoing structures, or added on by bondingadditional material, can increase stability of the bone void filler. Theridges or indentations may also help keep the bone filler material in adesired position during subsequent loading and/or healing of the treatedbone. Optional suction devices, preferably placed so that if at leastone such device is located approximate the lowest point of the cavitybeing formed, will desirably allow the cavity to be cleaned and/orpermit fluid or solids to be removed from and/or introduced into thecavity before filling.

[0052] Among the various embodiments of the present invention are thefollowing:

[0053] 1. A doughnut (or torus) shaped balloon with an optional built-insuction catheter to remove fat and other products extruded duringballoon expansion.

[0054] 2. A balloon with a spherical outer shape surrounded by aring-shaped balloon segment for body cavity formation.

[0055] 3. A balloon which is kidney bean shaped in configuration. Such aballoon can be constructed in a single layer, or several layers stackedon top of each other. This embodiment can also be a square or arectangle instead of a kidney bean.

[0056] 4. A spherically shaped balloon approximating the size of thehead of the femur (i.e. the proximal femoral epiphysis). Such a ballooncan also be a hemisphere.

[0057] 5. A balloon in the shape of a humpbacked banana or a modifiedpyramid shape approximating the configuration of the distal end of theradius (i.e. the distal radial epiphysis and metaphysis).

[0058] 6. A balloon in the shape of a cylindrical ellipse to approximatethe configuration of either the medial half or the lateral half of theproximal tibial epiphysis. Such a balloon can also be constructed toapproximate the configuration of both halves of the proximal tibialepiphysis.

[0059] 7. A balloon in the shape of a sphere on a base to approximatethe shape of the proximal humeral epiphysis and metaphysis with a plugto compress cancellous bone into the diaphysis, sealing it off. Such anembodiment can also be a cylinder.

[0060] 8. A balloon in the shape of a boomerang to approximate theinside of the femoral head, neck and lesser trochanter, allowing aprocedure to prevent hip fracture.

[0061] 9. A balloon in the shape of a cylinder to approximate the sizeand shape of the inside of the proximal humerus or of the distal radius.

[0062] 10. A balloon in the shape of a peanut or hourglass with aninternal membrane to constrain expansion preferentially along one ormore axes.

[0063] 11. A balloon in the shape of a disk.

[0064] 12. A balloon device with an optional suction device.

[0065] 13. Protective sheaths to act as puncture guard membersoptionally covering each balloon inside its catheter.

[0066] The present invention, therefore, provides improved, inflatabledevices for creating or enlarging a cavity or passage in a bone whereinthe devices are inserted into the bone. In various embodiments, theconfiguration of each device can be defined by the surrounding corticalbone and adjacent internal structures, and is designed to occupy up to70-90% of the volume of the inside of the bone, although balloons thatare as small as about 40% (or less) and as large as about 99% areworkable for fractures. In various other embodiments, the inflatedballoon size may be as small as 10% of the cancellous bone volume of thearea of bone being treated, such as for the treatment of avascularnecrosis and/or cancer, due to the localized nature of the fracture,collapse and/or treatment area. The fully expanded size and shape of theballoon is desirably regulated by material in selected portions of theballoon body whose resistance to expansion creates a restraint as wellas by either internal or external restraints formed in the deviceincluding, but not limited to, mesh work, webbing, membranes, partitionsor baffles, a winding, spooling or other material laminated to portionsof the balloon body, continuous or non-continuous strings across theinterior of the balloon held in place at specific locations by bondingto the inside of the balloon (by glue, welding, etc.) or by threadingthese strings through to the outside, and seams in the balloon bodycreated by bonding two pieces of body together or by bonding opposingsides of a body through glue or heat. Aside from the use of differentmaterials, the objectives of the present invention could similarly beaccomplished by utilizing different thicknesses of materials to regulatethe expansion of the balloon body. Moreover, the use of similarmaterials of differing elasticity, for example a polyurethane plasticballoon having discrete sections that are cross-linked by gammaradiation exposure and which are thus less prone to expansion, couldaccomplish the objectives of the present invention as well.

[0067] Spherical portions of balloons may be restrained by usinginelastic, semi-elastic, elastic and elastomeric materials in theconstruction of the balloon body, or may be additionally restrained asjust described. The material of the balloon can be a non-elasticmaterial, such as polyethylene tetraphthalate (PET), nylon, Kevlar® orother patented or nonpatented medical balloon materials. It can also bemade of semi-elastic materials, such as silicone, rubber, thermoplasticrubbers and elastomers or elastic materials such as latex orpolyurethane, if appropriate restraints are incorporated. The restraintscan be continuous or made of discrete elements of a flexible, inelastichigh tensile strength material including, but not limited to, thematerials described in U.S. Pat. No. 4,706,670, which is incorporatedherein by reference. The thickness of the balloon wall is typically inthe range of 2/1000ths to 25/1000ths of an inch, although otherthicknesses that can withstand increased pressures, such as 250-400 psior greater, even up to 500, 1000 or 2000 psi, may be used.

[0068] One important goal of percutaneous vertebral body augmentation ofthe present invention is to provide a balloon which can create a cavityinside the vertebral body whose configuration is optimal for supportingthe bone. Another important goal is to move the top and bottom of thevertebral body (otherwise known as the upper and lower endplates) towarda more normal anatomical position to restore height where possible. Bothof these objectives, however, are desirably achieved withoutsignificantly altering the outer dimensions of the sides of thevertebral body, either by fracturing the cortical sidewalls of thevertebral body or by moving already fractured bone in the sidewalls.

[0069] The present invention satisfies these goals through the design ofinflatable devices to be described. Inflating such a device desirablycreates a cavity within the calcium-containing soft cancellous bone(such as by compressing the cancellous bone) and/or desirably displacessurrounding cortical bone towards a more normal anatomical position.

[0070] In one embodiment, the balloon body desirably recreates the shapeof the inside of an unfractured vertebral body, and optimally grows nomore than a maximum of 70 to 90% of the inner volume. The balloons ofthese embodiments are inelastic, so designed such that maximallyinflating them will desirably recreate the predetermined shape and size.However, conventional balloons become spherical when inflated. Sphericalshapes do not typically permit the hardened bone void filler to supportthe spine adequately, because they can create a generally sphericalcavity which, when filled with filler material, makes single points ofcontact on the vertebral body surfaces (the equivalent of a circleinside a square, or a sphere inside a cylinder). In contrast, variousembodiments of the balloons of the present invention more generallyrecreate the flat surfaces of the vertebral body by incorporatingrestraints that maintain the balloon in desired shapes. These desiredshapes create cavities which, when filled with filler material,desirably distribute the load transferred from the vertebral bodysurfaces to the bone void fillers, which ultimately strengthens thespine. In addition, the volume of bone void filler that fills thesecavities desirably creates a thick mantle of cement (for example athickness of 4 mm or greater), which increases the compressive strengthof the filler material. Another useful feature of various embodiments isthe incorporation of ridges in the balloons which can leave one or moreimprints in the walls of the cavity created within the compressedcancellous bone. The resulting bone void filler “fingers” which willultimately fill these imprints can provide enhanced stability, andreduce the opportunity for the filler material to shift or displacewithin the vertebral body under compressive loading of the spine.

[0071] Balloons which can optimally compress cancellous bone invertebral bodies include the balloons listed as balloon types 1-3, 10and 12 above. Some of these balloons are desirably configured toapproximate the shape of the vertebral body. Since the balloon can bechosen to occupy less than the total inner volume (prior to fracture) ofthe targeted vertebral body, inflation of the balloon will desirably notexert undue pressure on the surrounding cortical sidewalls of thevertebral body (the sidewalls of the vertebral body will desirably notbe expand beyond their existing size either fractured or unfractured).However, since the upper and lower end plates of the vertebral body aretypically depressed in a compression fracture, and the balloon can beapproximately the height of an unfractured vertebral body, inflation ofthe balloon can move the top and bottom end plates back towards theirpre-fractured position and/or orientation. Moreover, a plurality ofindividual balloons can be utilized inside the vertebral body, such asby being stacked, and stacks containing any of the disclosed balloontypes can be mixed in shape and/or size to provide greater flexibilityand/or control.

[0072] A primary goal of percutaneous femoral (or humeral) headaugmentation (balloon type 4), percutaneous distal radius augmentation(balloon type 5), percutaneous proximal tibial augmentation (balloontype 6), and percutaneous proximal humeral augmentation (balloon type 7)is to create a cavity whose configuration is optimal to support the boneto be treated. Another important goal is to compress avascular (oraseptic) necrotic bone or to support avascular necrotic bone. Yetanother important goal is to help realign the fracture fragments. Thesegoals are generally achieved by exerting pressure primarily on thecancellous bone which may be transferred to the surrounding corticalbone. Pressure directly on a small section of the cortical bone couldconceivably cause worsening of the fracture, which, while not precluded,is desirably avoided. The design of various embodiments of theinflatable devices approximates the shape of the bone to be treated. Theapproximate volume of the cavity made by the inflatable device(s) can beas much as 70 to 90% of the volume of the bone to be treated. In thecase of avascular necrosis, depending upon the extent of the avascularnecrosis, a smaller or larger cavity inside bone will be formed. In somecases, if the area of avascular necrosis is small, a small balloon willbe utilized which might create a cavity only 10 to 15% of the totalvolume. If larger areas are involved with avascular necrosis, then oneor more larger balloons could be utilized which might create a muchlarger cavity, including cavities as large as 80 to 90% of the volume ofthe bone (or greater). The present invention satisfies these goalsthrough the design of the inflatable devices to be described.

[0073] For example, percutaneous hip augmentation (as shown inconnection with balloon type 8) is designed to prevent and/or treat hipfracture by compacting weak cancellous bone in the femur where hipfractures occur and replacing it with an appropriate supportingmaterial. The present invention satisfies this goal through the designof the inflatable devices to be described.

[0074] The present invention discloses improved systems for deploymentin bone comprising structures adapted to assume expanded geometrieshaving a desired configuration when used. These expandable structuresinclude material that allows the structure to differentially expand whenunder internal pressure. These structures, when in use, are able toexpand preferentially along one or more axes so as to deliver a greaterforce and/or displacement of cancellous bone towards one directionversus another. Furthermore, such structures, when distended, cangenerally match the geometry of the interior bone space in which thestructure is deployed, if desired. For example, such structures couldoptimally expand to a desired shape rather than simply towards areas oflowest bone density, i.e. expansion of the structure is can becontrolled even when encountering areas in the bone of varyingresistance.

[0075] Moreover, the exposure of the expandable structure to cancellousbone also typically requires materials having significant resistance tosurface abrasion, puncture and/or tensile stresses. For example,structures incorporating elastomer materials, e.g., polyurethane, whichhave been preformed to a desired shape, e.g., by exposure to heat andpressure, can undergo controlled expansion and further distention incancellous bone, without failure, while exhibiting resistance to surfaceabrasion and puncture when contacting cancellous bone.

[0076] The present invention further discloses inflatable devices thathave one or more biased directions of inflation. For example, inflatabledevices having reduced lateral growth may provide improved fracturereduction because such devices can exert a greater vertical force and/ordisplacement within the treated bone. Such inflatable devices may alsoprotect the lateral and anterior/posterior sidewalls of the vertebralbody by minimizing expansion towards these sidewalls and directingexpansion to a greater degree along the longitudinal axis of the spine.In situations where a surgical procedure is terminated when theinflatable device contacts a lateral cortical wall of the targeted bone,such biased expansion could permit improved fracture reduction prior toreaching this procedure endpoint.

[0077] Due to the nature of the injury, disease or other treatments, aswell as the health and age of the patient suffering from these injuries,it may be preferable to treat a bone with the devices of this inventionduring an open or semi-open surgical procedure. In addition, a goal ofthe surgery may be to replace the diseased or injured bone withmaterials (such as bone fillers or certain drugs) which do not flow, andwhich thus are not well suited for a more minimally invasive procedure.

[0078] A. Balloons for Vertebral Bodies

[0079] A first embodiment of the balloon (FIG. 1) constructed inaccordance with the teachings of the present invention is broadlydenoted by the numeral 10 and includes a balloon body 11 having a pairof hollow, inflatable parts 12 and 14 comprised of flexible material,including (but not limited to) non-elastic materials such as PET, mylaror Kevlarâ, elastic materials such as polyurethane, latex or rubber,semi-elastic materials such as silicone, or other materials. Parts 12and 14 have a suction tube 16 therebetween for drawing fats and otherdebris by suction into tube 16 for transfer to a remote disposallocation. Catheter 16 has one or more suction holes so that suction maybe applied to the open end of tube 16 from a suction source (not shown).

[0080] In this embodiment, the parts 12 and 14 are connected together byan adhesive which can be of any suitable type for adhering suchmaterials as well as by bonding, i.e. thermal bonding (laser,radio-frequency (RF)/induction, heated dies), ultrasonic welding,solvent bonding, etc. Parts 12 and 14 are doughnut-shaped as shown inFIG. 1 and have tubes 18 and 20 which communicate with and extend awayfrom the parts 12 and 14, respectively, to a source of inflating fluidunder pressure (not shown). The inflating fluid is preferably a liquid.The liquid inflates the balloon 10, particularly parts 12 and 14 thereofafter the balloon has been inserted in a collapsed condition (FIG. 8)into a bone to be treated, such as a vertebral bone 22 in FIG. 2. Theabove-mentioned U.S. Pat. Nos. 4,969,888 and 5,108,404, which areincorporated herein by reference, disclose the use of a guide pin andcannula for inserting the balloon into bone to be treated when theballoon is deflated and has been inserted into a tube and driven by thecatheter into the cortical bone where the balloon is inflated.

[0081]FIG. 8 shows a deflated balloon 10 being inserted through acannula 26 into bone. The balloon in cannula 26 is deflated and isforced through the cannula by exerting manual force on the catheter 21which extends into a passage 28 extending into the interior of the bone.The catheter is slightly flexible but is sufficiently rigid to allow theballoon to be forced into the interior of the bone where the balloon isthen inflated by directing fluid into the tube 88 whose outlet ends arecoupled to respective parts 12 and 14.

[0082] In use, the balloon 10 is initially deflated and, after the boneto be filled with the balloon has been prepared to receive the balloon(such as by punching, drilling or otherwise displacing a small amount ofthe cancellous bone directly beyond the opening of the cannula), thedeflated balloon is advanced into the bone in a collapsed conditionthrough the cannula 26. (The bone is shown in FIG. 2.) In thisembodiment, the balloon is oriented preferably in the bone such that theballoon expansion permits minimum pressure to be exerted on the corticalbone if there were no fracture or collapse of the bone. Where suchfracture or collapse has not occurred, such pressure would desirablycompress the bone marrow and/or cancellous bone against the inner wallof the cortical bone, thereby compacting the bone marrow of the bone tobe treated and to further enlarge the cavity in which the bone marrow isto be replaced by a biocompatible, flowable bone material.

[0083] The balloon is inflated to compact the bone marrow and/orcancellous bone in the cavity and, after compaction of the bone marrowand/or cancellous bone, the balloon is deflated and removed from thecavity. While inflation of the balloon and compaction occurs, fats andother debris may be removed from the space between and around parts 12and 14 by applying a suction force to catheter tube 16, if desired.Following this, and following the compaction of the bone marrow, theballoon is deflated and pulled out of the cavity by applying a manualpulling force to the catheter tube 21.

[0084] Another embodiment of an inflatable device constructed inaccordance with the teachings of the present invention is broadlydenoted by the numeral 60 and is shown in FIGS. 4 and 5. The balloon 60includes a central spherical part 62 which is hollow and which receivesan inflating liquid under pressure through a tube 64. The spherical partis provided with a spherical outer surface 66 and has an outer peripherywhich is surrounded substantially by a ring shaped part 68 having tubesegments 70 for inflation of part 68. A pair of passages 69 interconnectparts 62 and 68. A suction tube segment 72 draws liquid and debris fromthe bone cavity being formed by the balloon 60.

[0085] Provision can be made for a balloon sleeve 71 for the balloon 60as well as for all balloons disclosed herein. A balloon sleeve 71 (FIG.9) is shiftably mounted in an outer tube 71 a and can be used to insertthe balloon 60 when deflated into a cortical bone. The sleeve 71 hasresilient fingers 71 b which bear against the interior of the entranceopening 71 c of the vertebral bone 22 (FIGS. 9A and 9B) to preventrearing or bunching of the balloon 60. Upon removal of the balloonsleeve, liquid under pressure will be directed into the tube 64 whichwill inflate parts 62 and 68 so as to compact the bone marrow within thecortical bone. Following this, the balloon 60 is deflated and removedfrom the bone cavity.

[0086]FIGS. 6 and 6A show views of a modified doughnut shape balloon 80of the type shown in FIGS. 1 and 2, with one difference being thedoughnut shapes of the balloon 80 are not stitched onto one another. InFIG. 6, the balloon 80 has a pear-shaped outer convex surface 82 whichis made up of a first hollow part 84 and a second hollow part 85. A tube88 is provided for directing liquid into the two parts along branches 90and 92 to inflate the parts after the parts have been inserted into themedullary cavity of a bone. A catheter tube 16 is inserted into thespace 96 between two parts of the balloon 80. An adhesive bonds the twoparts 84 and 85 together at the interface thereof.

[0087]FIG. 6A shows one way in which the catheter tube 16 is insertedinto the space or opening 96 between the two parts of the balloon 80.

[0088]FIG. 7 shows the tube 88 of which, after directing inflatingliquid into the balloon 80, can inject contrast material into theballoon 80 so that x-rays can be taken of the balloon with the inflatingmaterial therewithin to determine the proper placement of the balloon.Alternatively, the inflation liquid could comprise a radiopaqueinflation liquid, such as Conray® contrast medium (commerciallyavailable from Mallinckrodt Inc. of St. Louis, Mo.), such that inflationand visualization can be done currently, allowing monitoring of theballoon position and condition during the inflation step. Tube 16 isalso shown in FIG. 6, it being attached in some suitable manner to theouter side wall surface of tube 88.

[0089] Still another embodiment of the invention is shown in FIG. 3,which is similar to FIG. 1 (although one difference it that it is not adoughnut) and includes an inflatable device 109 having three balloonunits 110, 112 and 114 which are inflatable and which have string-likerestraints 117 which limit the expansion of the balloon units in adirection transverse to the longitudinal axes of the balloon units. Ifdesired, the restraints can comprise the same or a similar material asthe balloon, or the restraints can comprise a material having a reduced,little or no substantial expansion capability.

[0090] A tube system 115 can be provided to direct liquid under pressureinto the balloon units 110, 112 and 114 so that liquid can be used toinflate the balloon units when placed inside the bone in a deflatedstate. Following the proper inflation and compaction of the bone marrow,the balloon(s) can be removed by deflating it/them and pulling it/themoutwardly of the bone being treated. The restraints desirably keep theopposed sides 77 and 79 substantially flat and parallel with respect toeach other.

[0091] In FIG. 10, another embodiment of the inflatable balloon isshown. The device comprises a kidney shaped balloon body 130 having apair of opposed kidney shaped side walls 132 which are adapted to becollapsed and to cooperate with a continuous end wall 134 so that theballoon 130 can be forced into a bone 136 shown in FIG. 11. A tube 138is used to direct inflating liquid into the balloon to inflate theballoon and cause it to assume the dimensions and location shown in thevertebral body 136 in FIG. 11. The balloon 130 will desirably compressthe cancellous bone if there is no fracture or collapse of the corticalbone. The restraints for this action are principally due to the side andend walls of the balloon.

[0092]FIG. 12 shows a balloon 140 which is also kidney shaped and has atube 142 for directing an inflatable liquid into the tube for inflatingthe balloon. The balloon is initially formed in a single chamber bladderbut the bladder can subsequently be branded and/or melted along curvedlines or strips 141 to form attachment lines 144 which take the shape ofside-by-side compartments 146 which are kidney shaped as shown in FIG.13. The branding desirably causes a welding and/or bonding of the twosides of the bladder—the material can be standard medical balloonmaterial, which is typically plastic that can be formed and/or bondedusing heat.

[0093]FIG. 14 is a perspective view of a vertebral body 147 containingthe balloon of FIG. 12, showing a double stacked balloon 140 when it isinserted in vertebral bone 147.

[0094]FIG. 15 is a view similar to FIG. 10 except that tufts 155, whichcan be string-like restraints or other structures between the opposinginner walls of the balloon, extend between and are connected to the sidewalls 152 of the inflatable device 150 and limit the expansion of theside walls with respect to each other. In this embodiment, the tuftsdesirably render the side walls generally parallel with each other. Ofcourse, tufts which merely limit and/or reduce the displacement betweenopposing walls of the balloon will similarly accomplish variousobjectives of the present invention to some degree. Tube 88 is used tofill the kidney shaped balloon with an inflating liquid in the mannerdescribed above.

[0095] The dimensions for a vertebral body balloon can vary across abroad range, depending upon the size, location, and condition of thetargeted vertebral body as well as the objectives of the treatment. Forexample, the height (H, FIG. 11) of a vertebral body balloon for bothlumbar and thoracic vertebral bodies can typically range from 0.5 cm to3.5 cm. The anterior to posterior (A, FIG. 11) vertebral body balloondimensions for both lumbar and thoracic vertebral bodies can typicallyrange from 0.5 cm to 3.5 cm. The side to side (L, FIG. 11) vertebralbody dimensions from thoracic vertebral bodies will often range from 0.5cm to 3.5 cm. The side to side vertebral body dimensions for lumbarvertebral bodies will typically range from 0.5 cm to 5.0 cm. Of course,depending upon the objectives of the treatment and the actual dimensionsof the patient's bones, the use of balloons having larger or smallerdimension than these disclosed ranges may be appropriate.

[0096] The eventual selection of the appropriate balloon for, forinstance, a given vertebral body is based upon several factors. Onemajor factor affecting the choice of balloon size is the objectives ofthe treatment. For example, if the principal treatment objective issimply the repair and/or augmentation of a collapsed vertebral body,then the appropriate balloon size (and desired cavity size) may be aballoon which approximates the size of the interior of the vertebralbody in an unfractured and/or uncollapsed condition. Alternatively, twoor more balloons could be used concurrently within a single vertebralbody, which together create a desired size cavity within the vertebralbody. As another alternative, if the objective of treatment is morelocalized within the bone, such as the creation of a smaller cavity toaugment and/or repair a smaller section of the bone, then the use of asmaller balloon size (and desired cavity size) may be desirous.Similarly, where the cancellous bone is relatively strong and/orresistant to compression, the use of a smaller balloon may be warrantedto accomplish the objective of displacing cortical bone (to reduce thefracture) without significantly compressing the cancellous bone (thuscreating a smaller cavity). Moreover, smaller balloons may also besuited for use in the treatment of bone tumors, etc., where the ballooncan be used to create a small cavity adjacent to the tumor—this smallcavity will simplify the use of other minimally invasive tools todirectly visualize the treatment area as well as morselize and/or excisethe tumor from the bone.

[0097] The anterior-posterior (A-P) balloon dimension is measured fromthe internal cortical wall of the anterior cortex to the internalcortical wall of the posterior cortex of the vertebral body. In general,for augmentation and/or reinforcement of a collapsed vertebral body, theappropriate A-P balloon dimension will often be approximately 5 to 7millimeters less than this measurement.

[0098] The appropriate side to side balloon dimensions for a givenvertebral body is selected from the CT scan or from a plain film x-rayview of the vertebral body to be treated. The side to side distance canbe measured from the internal cortical walls of the side of thevertebral bone. In one embodiment, the appropriate side to side balloondimension may be 5 to 7 millimeters less than this measurement. Inalternate embodiments, the appropriate side to side balloon dimensionsmay be significantly smaller, such as where multiple balloons areintroduced into a single vertebral body or where the displacement ofcortical bone is a primary objective of the treatment. In general,lumbar vertebral bodies tend to be much wider in their side to sidedimension than in their A-P dimension. In contrast, thoracic vertebralbodies are typically approximately equal in their the side to sidedimensions and their A-P dimensions.

[0099] The height dimensions of the appropriate vertebral body balloonfor a given vertebral body may be chosen by the CT scan or x-ray viewsof the vertebral bodies above and below the vertebral body to betreated. The height of the vertebral bodies above and below thevertebral body to be treated can be measured and averaged. This averagemay be used to determine the appropriate height dimension of the chosenvertebral body balloon. Of course, as previously mentioned, variousother balloon sizes may be desirous based upon the objectives of thetreatment, as well as the actual patient's anatomy.

[0100] B. Balloons for Long Bones

[0101] Long bones which can be treated with the use of balloons of thepresent invention include (but are not limited to) the distal radius(larger arm bone at the wrist), the proximal tibial plateau (leg bonejust below the knee), the proximal humerus (upper end of the arm at theshoulder), and the proximal femoral head (leg bone in the hip).

[0102] C. Distal Radius Balloon

[0103] For the distal radius, one embodiment of a balloon 160 is shownin the distal radius 152 has a shape which approximates a pyramid butmore closely can be considered the shape of a humpbacked banana in thatit substantially fills the interior of the space of the distal radius toforce cancellous bone 154 against the inner surface 156 or cortical bone158.

[0104] The balloon 160 has a lower, conical portion 159 which extendsdownwardly into the hollow space of the distal radius 152, and thisconical portion 159 increases in cross section as a central distalportion 161 is approached. The cross section of the balloon 160 is shownat a central location (FIG. 17B) and this location is near the widestlocation of the balloon. The upper end of the balloon, denoted by thenumeral 162, converges to the catheter 88 for directing a liquid intothe balloon for inflating the same to compress the cancellous boneand/or force the cancellous bone against the inner surface of thecortical bone. The shape of the balloon 160 is desirably predeterminedand can be restrained by tufts formed by string restraints 165, as wellas various other types of restraints described herein. These restraintsare optional and provide additional strength to the balloon body 160,but are not absolutely required to achieve the desired configuration.The balloon is placed into and taken out of the distal radius in thesame manner as that described above with respect to the vertebral bone.

[0105] The dimensions of the distal radius balloon vary as follows:

[0106] The proximal end of the balloon (i.e. the part nearest the elbow)is cylindrical in shape and will vary from 0.5′0.5 cm to 1.8′1.8 cm.

[0107] The length of the distal radius balloon will vary from 1.0 cm to12.0 cm.

[0108] The widest medial to lateral dimension of the distal radiusballoon, which occurs at or near the distal radio-ulnar joint, willmeasure from 1.0 cm to 2.5 cm.

[0109] The distal anterior-posterior dimension of the distal radiusballoon will vary from 0.5 cm to 3.0 cm.

[0110] In an alternate embodiment also suited for use in treating adistal radius fracture, a balloon can take the shape of a toroidal ordisk-like shape, such as shown in FIGS. 25A-25C.

[0111] D. Proximal Humerus Fracture Balloon

[0112] The selection of the appropriate balloon size to treat a givenfracture of the distal radius will often depend on the radiological sizeof the distal radius and the location of the fracture, as well as thetreatment goals.

[0113] In the case of the proximal humerus 169, one embodiment of aballoon 166 shown in FIG. 18 is spherical and has a base design. It canoptimally compact the cancellous bone 168 in a proximal humerus 169. Amesh 170, embedded, laminated and/or wound, may be used to form a neck172 on the balloon 166, and a second mesh 170 a may be used to conformthe bottom of the base 172 a to the shape of the inner cortical wall atthe start of the shaft. These restraints provide additional strength tothe balloon body, but the configuration can be achieved through variousmethods, including molding of the balloon body or various otherrestraints described herein. This embodiment desirably compresses thecancellous bone to create a compacted region surrounding the balloon 166as shown in FIG. 18. The cortical bone 173 is desirably relatively wideat the base 174 and is thin-walled at the upper end 175. The balloon 166has a feed tube 177 into which liquid under pressure is forced into theballoon to inflate it to compact the cancellous bone in the proximalhumerus. The balloon is inserted into and taken out of the proximalhumerus in the same manner as that described above with respect to thevertebral bone.

[0114] In this embodiment, the dimensions of the proximal humerusfracture balloon vary as follows:

[0115] The spherical end of the balloon will vary from 1.0′1.0 cm to3.0′3.0 cm.

[0116] The neck of the proximal humeral fracture balloon will vary from0.8′0.8 cm to 3.0′3.0 cm.

[0117] The width of the base portion or distal portion of the proximalhumeral fracture balloon will vary from 0.5′0.5 cm to 2.5′2.5 cm.

[0118] The length of the balloon will vary from 4.0 cm to 14.0 cm.

[0119] The selection of the appropriate balloon to treat a givenproximal humeral fracture depends on the radiologic size of the proximalhumerus and the location of the fracture as well as the treatment goals.

[0120] E. Proximal Tibial Plateau Fracture Balloon

[0121] The tibial fracture is shown in FIG. 19A in which one embodimentof a balloon 180 is placed in one side 182 of a tibia 183. Desirably,the balloon, when inflated, compacts the cancellous bone in the layer184 surrounding the balloon 180. A cross section of this embodiment of aballoon is shown in FIG. 19C wherein the balloon has a pair of opposedsides 185 and 187 which are interconnected by restraints 188 which canbe in the form of strings or flexible members of any suitableconstruction. In this embodiment, the restraints desirably maintain thesides 185 and 187 substantially parallel with each other andnon-spherical. A tube 190 is coupled to the balloon 180 to directinflation liquid into and out of the balloon. The ends of the restraintsare shown in FIGS. 19B and 19D and denoted by the numeral 191. Theballoon is inserted into and taken out of the tibia in the same manneras that described above with respect to the vertebral bone. FIG. 19Bshows a substantially circular configuration for the balloon; whereas,FIG. 19D shows a substantially elliptical version of the balloon.

[0122] The dimensions of this embodiment of a proximal tibial plateaufracture balloon vary as follows:

[0123] The thickness or height of the balloon will vary from 0.5 cm to5.0 cm.

[0124] The anterior-posterior (front to back) dimension will vary from1.0 cm to 6.0 cm.

[0125] The side to side (medial to lateral) dimension will vary from 1.0cm to 6.0 cm.

[0126] The selection of the appropriate balloon to treat a given tibialplateau fracture will depend on the radiological size of the proximaltibial and the location of the fracture, as well as the treatment goals.

[0127] F. Femoral Head Balloon

[0128] In the case of the femoral head, one embodiment of a balloon 200is shown as having been inserted inside the cortical bone 202 of thefemoral head which is thin at the outer end 204 of the femur and whichcan increase in thickness at the lower end 206 of the femur. Thecortical bone surrounds the cancellous bone 207 and this bone isdesirably compacted by the inflation of the balloon 200. The tube fordirecting liquid for inflation purposes into the balloon is denoted bythe numeral 209. It extends along the femoral neck and is directed intothe femoral had which is generally spherical in configuration. FIG. 20Ashows that the balloon, denoted by the numeral 200 a, can behemispherical as well as spherical, as shown in FIG. 20. The balloon 200is inserted into and taken out of the femoral head in the same manner asthat described with respect to the vertebral bone. The hemisphericalshape is maintained in this example by bonding overlapping portions ofthe bottom, creating pleats 200 b as shown in FIG. 20A.

[0129] The dimensions of the femoral head balloon may vary asfollows—the diameter of the femoral head balloon will vary from 1.0 cmto up to 4.5 cm or greater. The appropriate size of the femoral headballoon to be chosen depends on the radiological or CT scan size of thehead of the femur and the location and size of the avascular necroticbone. The dimensions of the hemispherical balloon are similar to thoseof the spherical balloon, except that approximately one half of theballoon is provided.

[0130] G. Prevention of Hip Fracture

[0131]FIG. 21 illustrates one embodiment of a “boomerang” balloon 210adapted for preventing and/or treating hip fracture. When inflated, the“boomerang” balloon 210 is a cylinder which gradually bends in themiddle, like a boomerang, and extends from about 0.5 cm from the end ofthe femoral head 211 through the femoral neck 212 and down into theproximal femoral diaphysis 213 about 5-7 cm past the lesser trochanter214. This embodiment of a balloon 210 preferably maintains its shape byrings of inelastic material (215 is one of them) held closer together onone side by attachment to a shorter inelastic band 216 running thelength of the side of balloon and further apart by attachment to alonger inelastic band 217 bonded on the opposite side, although variousother restraints disclosed herein would also suffice.

[0132] After and prior to inflation, the balloon 210 may be folded back(shown in dotted lines at 218) against the inflation tube 219. Prior toinflation, the balloon 210 can also be rolled up and held against theinflation tube with loose attachments that break when the balloon isinflated. To insert the balloon on its inflation tube into the hip, thesurgeon can use a power drill under radiographic guidance to create acavity 220 that is usually 4-6 mm wide starting at the lateral femoralcortex 221 and proceeding into the femoral head 211. Inflation of theballoon 210 into the greater trochanteric region 222 instead of down thefemoral diaphysis 213 is less desirable and is typically avoided byproper choices in the shape of the balloon as well as by its placementand correct orientation (the deflated balloon desirably facing thelesser trochanter). After the balloon 210 has been inflated within thecavity 220 (see the dotted lines in FIG. 21), the predetermined size andshape of the balloon biases the proximal portion of the balloon downwardinto the lesser trochanter. Optionally, a second cavity can be drilleddown into the diaphysis, starting from the same entry point or from theother side.

[0133] Patients with bone density in the hip below a threshold value areat increased risk of hip fracture, and lower densities create greaterrisk. Patient selection may be done through a bone density scan or othermethods of determining bone quality well known in the art. Suchselection could also result from a previous and/or concurrent fractureof the other hip, or some other type and/or location of osteoporoticfracture. The balloon length can be chosen by the surgeon to extendabout 0.5 cm from the end of the femoral head, through the femoral neckand into the proximal femoral diaphysis, usually about 4-8 cm below thelesser trochanter. The balloon diameter can be chosen by measuring theinner cortical diameter of the femoral neck (the most narrow area) andsubtracting 0.5 cm. The preferred dimensions of the “boomerang” balloonare a total length of 10-20 cm and a diameter of 1.0-2.5 cm. (A“humpback banana” balloon with appropriate length may also be useful inhip fracture prevention, where the “humpback” width does not exceed thedesired femoral neck dimensions.)

[0134] Patients having the lowest bone densities in the femoral head mayrequire greater compacting in the femoral head, which may, for example,be provided by using two balloons, one after the other: the “boomerang”followed by the femoral head balloon (inserted at the same point andexpanded prior to inserting any supporting material.) Alternatively, the“boomerang” balloon may be adapted to have a distal portion thatapproximates the shape of the femoral head balloon.

[0135] The various balloons described herein could also be used inconjunction with the replacement of various structures within human andanimal bodies. For example, the balloons described herein could be usedto compress cancellous bone in a femur in preparation for theimplantation of an artificial hip stem similarly, the balloons describedherein could be used in conjunction with various other joint replacementprocedures, including artificial knee and ankle joints.

[0136] H. All Balloons

[0137] It should be understood that the various embodiments of balloonsdisclosed herein are by no means limited in their utility to use in asingle treatment location within the body. Rather, while each embodimentmay be disclosed in connection with an exemplary treatment location,these embodiments can be utilized in various locations within the humanbody, depending upon the treatment goals as well as the anatomy of thetargeted bone. For example, the embodiment of a balloon previouslydisclosed as useful in treating a fracture of the distal radius couldsimilarly be used in the treatment of fractures in various other areaswithin the body, including but not limited to fractures and/or impendingfractures of the femur, the radius, the ulna, the tibia, the humerus,the calcaneus or the spine. Similarly, the various other disclosedembodiments can be utilized throughout the body, with varying resultsdepending upon treatment goals and/or the anatomy of the targeted bone.

[0138] II. The Inflatable Device

[0139] A. Complex Expandable Structures

[0140] Sometimes it can be difficult to achieve a desired uniformity andarea of compaction within a given cancellous bone region using anexpandable body having a single expansion region. FIG. 27 shows acomplex preformed structure 280 which includes expanded segmentedregions 282 and 284 spaced along its length. The structure 280 providesa longer profile along which volume can be increased.

[0141] The complex expandable structure is created by extruding ormolding a tube 286 of polyurethane plastic or other elastomer material.In a preferred embodiment, the tube is comprised of polyurethane plasticmaterial. The tube has a normal extruded wall thickness (T5) and anormal extruded outside diameter (D5) (as shown in FIG. 27).

[0142] The segmented shaped regions 282 and 284 are created by exposingan intermediate region of the tube to heat, positive interior pressureand/or stretching inside a fixture or mold (not shown). In oneembodiment, the fixture could possess two cavity regions separated by areduced diameter region or intermediate channel. The cavity regions andthe channel can be exposed to a source of heat, to soften the materialof the region. When heat-softened (in the manner previously described),the interior of the tube 286 is stretched and subjected to positivepressure from a source. The material in the region 288 will desirablyexpand or extend within the cavities and the channel.

[0143] Once cooled and removed from the fixture, the structure 280 canbe attached to the distal end of an outer catheter tube 250. (See FIG.28.) The structure of the outer catheter tube 250 (as well as the innercatheter tube 258) can vary, and the outer catheter tube 250 cancomprise various flexible materials, including medical grade plasticmaterials like vinyl, polyethylenes, ionomer, polyurethane, andpolytetrapthalate (PET) as well as less flexible materials such asKevlar®, PEBAX™, stainless steel, nickel-titanium alloys, and othermetals and/or ceramics. The outer catheter tube 250 desirablyincorporates an interior bore 260, into which an inner catheter tube 258extends. It should be appreciated that the outer catheter tube 250 canhave one or more interior lumens. In the illustrated embodiment, theinner catheter tube 258 extends through the interior bore 260 and beyondthe distal end 254 of the catheter tube 250. A distal end region of thestructure 280 is secured to the to the distal end region 254 of theouter catheter tube 250, while a proximal end region of the structure280 is secured to the distal end region 262 of the inner catheter tube258. The end regions can be secured, e.g., using adhesive or thermalbonding, etc.

[0144] The structure 280 possesses, in an open air environment, a normalexpanded shape, having diameter D7 (shown in phantom lines of FIG. 27).The normal shape and diameter D7 for the regions 282 and 284 generallycorrespond with the shape and dimension of the cavities, respectively.

[0145] When an interior vacuum is drawn, removing air and/or fluid fromthe structure 280, the structure 280 assumes a substantially collapsed,and not inflated, geometry, shown as lines D6 in FIG. 27. Due to theapplication of heat and pressure upon the intermediate region 288, thediameter D6 for each region 282 and 284 is larger than the normallyextruded or molded outside diameter D5 of the original extruded tube.

[0146] The regions 282 and 284 are separated by a tubular neck 298,which segments the structure 280 into two expandable regions 282 and284. When substantially collapsed under vacuum or not inflated, thestructure 280 exhibits a low profile, ideal for the insertion intoand/or removal from the targeted cancellous bone region.

[0147] The introduction of fluid volume back into the tube 286 willcause each region 282 and 284 to return from the collapsed diameter D6to the normal, enlarged, but not distended, geometry, having the shapeand diameter shown in phantom lines D7 in FIG. 27.

[0148] In the illustrated embodiment, the first and second shapedregions 282 and 284 have generally the same radius of expansion and thusthe same non-distended shape and diameter D7. Alternatively, each region282 and 284 can have a different radius of expansion, and thus adifferent non-distended shape and diameter. Regardless, when in thenormal, non-distended diameter D7, the material of the structure 280 inthe region 288 is not significantly stretched or stressed, because theregions 282 and 284 have been expanded in a stress-relieved conditioninto these geometries in the cavities.

[0149] As before explained in conjunction with the structure, theregions 282 and 284 can be shaped by heat and/or interior pressurewithin different cavities to assume different geometry's, e.g.,cylindrical or elliptical geometry, or a non-spherical, non-cylindrical,or non-elliptical geometry, with either uniform or complex curvature,and in either symmetric or asymmetric forms. Of course, more than twosegmented regions 282 and 284 can be formed along the length of thetube. In addition, the normally expanded shape characteristics of thestructure can be achieved by other techniques. For example, and not byway of limitation, the structure can be formed by dipping, lost waxcasting, or injection molding.

[0150] Each shaped region 282 and 284 possesses a minimum wall thickness(designated T7 in FIG. 27) when in the normally enlarged but notdistended geometry D7. Due to expansion of heat-softened material underpressure in the cavities, the wall thickness is not uniform, i.e., T7 isless than the normal extruded or molded wall thickness T5 of the tube.The minimum wall thickness T7 for the regions 282 and 284 can be thesame or different.

[0151] When in the enlarged, but not distended geometry, the neck region298 has an outside diameter (designated D9 in FIG. 27), which is equalto or greater than the normal extruded or molded diameter D5 of thetube. The size of the channel in the fixture determines the magnitude ofthe diameter D9. Due to expansion of heat-softened material in theadjacent regions 282 and 284 under pressure in the cavities, the neckregion 298 (which expands under pressure in the channel) has a wallthickness (designated T9 in FIG. 27) which is less than or equal to thenormal extruded or molded wall thickness T5 of the tube 286, but stillgreater than the minimum wall thickness T7 of either fully shaped region282 or 284.

[0152] The formed complex structure 280 thus possesses regions ofnon-uniform minimum wall thickness along its length; that is, T5≧T9≧T7.The formed complex structure 280 also provides multiple expandableregions 282 and 284 of the same or different enlarged outside diameters(D7), segmented by a neck region 298, in which D6>D5; D7>D6; and D7>D9.

[0153] By continuing to apply fluid volume at a constant pressure at athreshold amount P(t), and thereby increasing the volume within thestructure 280, the shaped regions 282 and 284 of the structure 280 willcontinue to enlarge beyond diameter D7 to a distended shape andgeometry, designated D8 in FIG. 27. The wall thickness T7 furtherdecreases and approaches T8. As the regions 282 and 284 approachdiameter D8, the diameter D9 of the neck region 298 will likewiseincrease toward diameter D10, as FIG. 27 shows, providing more uniform,elongated surface contact with cancellous bone.

[0154] Enlargement of the structure 280 beyond diameter D7 stretches thematerial in the regions 282, 284 and 298 beyond their stress-relievedcondition, although the distended geometry of the regions 282 and 284will, in important respects, maintain the preformed shape dictated bythe cavities.

[0155] The degree of stretching at a substantially constant incrementalpressure condition can be tailored to achieve a desired, fully distendeddiameter D8. The final, fully distended diameter D8 can be selected tomatch the dimensions of the targeted cancellous bone region. Thecontrolled stretching of the segmented regions 282 and 284 in tandem canprovide an equal volume compression of cancellous bone with a majordiameter that is less than a single non-segmented region (i.e., onewithout the neck region 298). Stated another way, segmented regions 282and 284, when expanded to a given inflation volume, have a diameter lessthan a sphere expanded to an equal inflation volume.

[0156] While expanding in the region between D7 and D8, the structure280, when inside bone, assumes an increasingly larger surface area andvolume, thereby compacting surrounding cancellous bone. Inflation incancellous bone may occur at the same threshold pressure P(t) as outsidebone. However, an increase in the threshold pressure P(t) inside bone istypically required, due to the density of the cancellous bone andresistance of the cancellous bone to compaction.

[0157] B. Assembly of an Expandable Balloon Device with an InternalMembrane

[0158]FIGS. 23 and 24A-24C depict cross-sectional views of anotheralternate embodiment of a cavity-forming device constructed inaccordance with the teachings of the present invention. Because many ofthe features of this embodiment are similar to those described inconnection with the previous embodiment, like reference numerals will beused to describe similar components.

[0159] In this embodiment the cavity-forming device incorporates aballoon 300 comprising a section of dual lumen tubing having an outerwall 310 and an internal membrane 320. The balloon 300 will desirablycomprises a material that is commonly used for balloon cathetersincluding, but not limited to, polyethylene, mylar, rubber orpolyurethane. Even more desirably, the balloon 300 will comprise anelastomer material, which also possess the capability of beingpreformed, i.e., to acquire a desired shape by exposure, e.g., to heatand pressure, e.g., through the use of conventional thermoforming, blowmolding and/or dip coating techniques. Candidate materials that meetthis criteria include polyurethane, silicone, thermoplastic rubber,nylon, and thermoplastic elastomer materials.

[0160] In the illustrated embodiment, the balloon 300 comprises TEXIN®5290 polyurethane plastic material (commercially available from BayerCorp.). This material can be processed and extruded in a tubular shape,which can then be cut into individual lengths for further processing.The balloon 300 can be formed by exposing a cut tube length to heat andthen enclosing the heated tube within a mold while positive interiorpressure is applied to the tube length. For example, one embodiment of aballoon can be formed by heating a length of extruded tubing(incorporating an internal membrane 320) to 320° F. for approximately220 seconds, and then stretching the tubing by 10 mm while the tubing isblown at 100 psi in a mold for 45 seconds. The mold can of course bepart of a conventional balloon forming machine

[0161] In the present embodiment, after the balloon is formed theproximal end of the balloon 300 can be attached to the distal end of anouter catheter body 250 and the distal end of the balloon 300 can beattached to the distal end of an inner catheter body 258. The outer andinner catheters may each comprise extruded tubing made, e.g., fromTEXIN® polyurethane plastic material, and each can extruded in a tubularshape using, e.g., a screw type extrusion machine, with a GENCA™ head,using suitable screens.

[0162] In assembling the cavity-forming device, the proximal end of theballoon 300 is desirably bonded to the distal end of an outer catheterbody 250, as FIG. 26A shows. In one preferred embodiment (as FIG. 26Bshows), a razor blade or other cutting instrument can be used to splitapproximately 5 mm of the distal end of the outer catheter body 250,creating a pair of slots 360, as best shown by “A” in FIG. 26B. Theproximal end of the balloon 300 can then be slid over the distal end ofthe outer catheter body 250, with the outer wall 310 positioned aroundthe distal tip of the outer catheter body 250 and the internal membrane320 positioned within the slots 360 (as FIG. 26C shows). To maintain theflow channels (for the inflation fluid) through the outer catheter body250 and into the balloon 300, a pair of mandrels or inserts (not shown)can be introduced into the outer catheter body and balloon in a mannerwell known in the art. The distal end of the outer catheter body 250 andthe proximal end of the balloon 300 can then be bonded together usingvarious means including heat bonding, adhesives, or the like. After thebond is formed, the mandrels can be removed. Desirably, the splitting ofthe outer catheter body 250 increases the mechanical strength of thebond between the catheter body 250 and the balloon 300 and permits theballoon to be more securely bonded to the outer catheter body 250,reducing the opportunity for a proximal bond failure of the balloon 300.

[0163] The distal end of the balloon 300 is also bonded to the distalend of an inner catheter body 258. If desired, the distal end of theinner catheter body 258 may be split in a similar manner to increase themechanical strength of the distal bond. Desirably, the inner catheterbody 258 will extend through the outer catheter body 250 and the balloon300 along one side the internal membrane 320.

[0164] As FIG. 26A shows, the proximal end of the outer catheter body250 can be secured to a distal end of a y-shaped luer fitting 400. Theinner catheter body 258 desirably extends through an inner lumen of theluer fitting 400, and may be bonded to a proximal end of the fitting400. Desirably, an inflation fitting 402 of the y-shaped luer fitting400 will be in fluid communication with the lumen 404 (see FIG. 26C)formed between the inner and outer catheter bodies 250 and 258, whichwill in turn be in fluid communication with the interior of the balloon300, such that an inflation fluid introduced into the inflation fitting402 will inflate the balloon 300.

[0165] Desirably (as FIGS. 26A to 26C show), the outer catheter body 250and/or y-shaped luer fitting 400 will incorporate a marker 406 or otherexternally viewable indicia which shows a physician the orientation ofthe internal membrane 320 when the balloon 300 is in a desired positionwithin the patient. Such indicia could include colored markers orstripes 406, indentations and/or protrusions on the outer catheter body250 or y-shaped luer fitting 400 as well as the orientation of the luerfitting itself. By utilizing such indicia 406, the physician can easilyrotate the balloon 300 to a desired orientation within the vertebralbody. Because the materials used in constructing medical balloons aretypically radio-lucent, it would be difficult to gage the orientation ofthe internal membrane 320 once the balloon 300 is in position within thetargeted bone. Alternatively, or in combination with external indicia406, the internal membrane 320 could incorporate one or more markerbands or other radiopaque substances 408 (see FIG. 26C) to depict theorientation of the membrane 320 within the targeted vertebral body.

[0166] Various materials can be selected for the component parts of thecavity-forming device. Furthermore, the dimensions of the componentparts of the cavity-forming device can also vary, according to itsintended use. It should also be understood that, while one describedembodiment incorporates dual lumen tubing, various other embodimentscould incorporate other types of multi-lumen tubing (including, but notlimited to triple, quadruple, etc., lumen tubing), as well as couldincorporate membrane(s) having varying orientations and/or positionswithin the tubing (e.g., symmetrical or asymmetrical).

[0167] The following table lists preferred component materials anddimensions, which are well suited for a cavity-forming device(incorporating dual lumen tubing) that can be deployed for use in avertebral body: Component Material Dimension Outer catheter PolyurethaneOutside Diameter: 0.124″ body Plastic Inside Diameter: 0.102″ Innercatheter Polyurethane Outside Diameter: 0.035″ body Plastic InsideDiameter: 0.025″ Expandable Structure: Extruded Tubing: PolyurethaneOuter Diameter: 0.164″ Plastic Outer Wall Thickness: 0.028″ MembraneThickness: 0.030″ Longitudinal Length of Balloon 0.600″ to 0.949″

[0168] C. Exemplary Performance Features of the Expandable Balloon

[0169]FIGS. 24A, 24B and 24C show cross-sectional views of thepreviously-described embodiment of a balloon 300 during its deploymentin air. Desirably, the balloon 300 will expand in a similar fashionwithin the targeted bone such as a vertebral body.

[0170]FIG. 24A depicts a cross-sectional view of the balloon 300 whenfilled with a small amount of inflation fluid, such that the balloondesirably assumes the approximate size and shape of the mold in whichthe balloon was previously formed, with minimal stresses experienced bythe internal membrane 320. In this condition, the expansion of theballoon is substantially circular in cross-section. Accordingly, thevertical and horizontal dimensions of the cross-section of the expandedballoon 300 are approximately equal, or DX1=DY1.

[0171]FIG. 24B depicts the balloon 300 of FIG. 24A when further filledwith a pressurized inflation fluid. In this figure, the balloon 300 hasassumed a further distended shape, with the wall material of the balloon300 typically undergoing elastic and/or plastic deformation to assumethis enlarged geometry. The balloon 300 desirably does not assume acompletely circular cross-sectional shape, principally because theinternal membrane resists lateral expansion of the outer walls 310.While some elongation of the internal membrane 320 typically occurs (dueto elastic and/or plastic deformation of the membrane), the resultingcross-sectional shape is generally ovoid or somewhat similar to afigure-8. The balloon 300, however, is not as significantly restrainedfrom growing in the vertical direction. This combination of restraintsresults in a balloon which substantially expands or grows more in thevertical direction than in the horizontal direction. Accordingly, thevertical dimension of the expanded balloon 300 is larger than thehorizontal dimension of the balloon 300, or DX2>DY2.

[0172]FIG. 24C depicts the balloon 300 of FIGS. 24A and 24B when furtherfilled with a pressurized inflation liquid. In this figure, the balloon300 has assumed an even more distended shape, with the wall materialtypically having undergone both elastic and significant plasticdeformation in order to assume this enlarged geometry. At this point,the balloon 300 is clearly in a non-circular shape, with the internalmembrane 320 significantly resisting lateral growth of the balloon(although some additional elastic stretching and/or plastic deformationof the membrane 320 has likely occurred). Accordingly, the verticaldimension of the expanded balloon 300 is significantly larger than thehorizontal dimension of the balloon 300, or DX3>>DY3.

[0173] For the above-described embodiment, an experimental inflation ofthe balloon with inflation fluid with volumes of 0 cc to 2 cc and 2 ccto 4 cc produced the following results:

0 cc

[0174] Balloon Minor diameter (DX1 —width): 7.7 mm

[0175] Balloon Major diameter (DY1—height): 7.7 mm

Inflation to 2 cc (Fluid)

[0176] Balloon Minor diameter (DX2—width): 9.2 mm

[0177] Increase in minor (horizontal) diameter: 1.5 mm (width)-[19.5%total increase]

[0178] Balloon Major diameter (DY2—height): 10.9 mm

[0179] Increase in major (vertical) diameter: 2.2 mm (height)−[28.6%total increase]

Inflation to 4 cc (Fluid)

[0180] Balloon Minor diameter (DX3—width): 12.7 mm

[0181] Increase in minor (horizontal) diameter: 5 mm (width)−[65% totalincrease]

[0182] Balloon Major diameter (DY3—height): 15.4 mm

[0183] Increase in major (vertical) diameter: 7.7 mm (height)−[100%total increase]

[0184] In addition to axial growth of the balloon 300 as the balloonexpands (as previously described), the longitudinal length of a balloonalso tends to increase during inflation. This is because the stressesexperienced by the balloon material are typically acting in more thanone dimension (resulting in material deformation along more than asingle axis), causing the overall longitudinal length of the balloon 300to expand in response to the increased internal pressure. In the presentembodiment, however, the internal membrane 320 also tends to reduce thelongitudinal growth of the balloon during inflation. For example, forthe previously described embodiment of a balloon 300, a volumetricincrease from 2 cc to 4 cc results in a longitudinal length increase forthe balloon of only 27.1%. For a similarly constructed balloon that doesnot incorporate an interior membrane, a volumetric increase from 2 cc to4 cc results in a longitudinal length increase of 37.1%. Accordingly,the interior membrane 320 of the present invention restrains not onlycertain aspects of circumferential expansion, but also restrains aspectsof longitudinal expansion as well.

[0185] The internal membrane 320 of the present embodiment alsosignificantly reduces the opportunity for the balloon 300 to experiencea complete radial failure and/or fragment within the patient. During asurgical procedure, if the balloon is punctured or torn, the balloonfailure may propagate through a significant amount of the balloonmaterial. If this failure propagates around the entire radius of theballoon, then the distal section of the balloon is in danger of becomingcompletely separated from the proximal end of the balloon, with only theinner catheter body 258 connecting the distal section of the balloon tothe cavity-forming device. In such a case, upon removal of the cavityforming device from the patient, it is possible for the inner catheterbody 258 to fail, leaving the distal section and any balloon fragmentsin the patient.

[0186] The internal membrane 320 of the present embodiment desirablyreduces any opportunity for a complete radial failure of the balloon300, and also significantly reduces the opportunity for balloonfragments to separate from the cavity-forming device. Where the interiormembrane 320 joins the expandable wall, the geometry and/or additionalthickness of balloon material at this junction 410 (see FIG. 26C)significantly increases the balloon's resistance to fracture at hislocation. A fracture which propagates towards such a junction 410 willtypically be redirected by the junction—typically the fracture willeither terminate, will rebound from the junction and/or will beredirected along the junction.

[0187] In the disclosed embodiment, a radial fracture which propagatestowards the junction 410 will generally be redirected towards thelongitudinal axis of the balloon 300. Moreover, the interior membrane320 serves to connect the proximal and distal ends of the balloon 300,which will reinforce the inner catheter body 258 in the unlikely eventof a complete radial failure of the balloon. Accordingly, because thepresent embodiment incorporates at least two longitudinally extendingjunctions (i.e., the internal membrane 320 of the balloon 300 and theinner catheter body 258 to which the distal end of the balloon 300 issecured), a fracture of this embodiment is unlikely to result in acomplete radial tear of the balloon material and/or fragmentation of thecavity forming device.

[0188] III. Implant Creation and Performance

[0189] Once the balloon 300 is in a desired position within a targetedbone (in this example a vertebral body), an inflation medium can beintroduced into the balloon, which desirably expands the balloon withinthe targeted bone. The balloon will desirably assume a similar shapewithin the targeted bone as it would in air, thereby creating a cavitywithin the bone that is substantially the same shape and size as theinflated balloon. It must be understood, however, that variations incancellous bone density and quality may distort the final expanded sizeand shape of the inflated balloon, such that the expanded balloon may besignificantly different in size and shape than it would be when expandedin air.

[0190] While the restraints described herein may not absolutelyguarantee that the final shape and size of the balloon (and thus thecavity) will be identical to the shape and size of the balloon in air,the restraints described herein significantly increase the potential forcreating an optimally sized and shaped cavity to achieve one or moredesired treatment goals. For example, if the desired treatment goal isthe reinforcement and/or repair of a targeted vertebral body, a balloonmay be chosen that incorporates restraints to maximize vertical growthof the balloon (in this context, the vertical orientation can be assumedto be parallel to the longitudinal axis of the spine) while minimizinghorizontal and/or longitudinal growth of the balloon. If desired, thisballoon could also incorporate restraints that reduce and/or minimizeballoon expansion along its longitudinal axis.

[0191] Alternatively, a physician may desire a balloon that incorporatesrestraints to maximize horizontal growth of the balloon (in thiscontext, horizontal growth can be assumed to be transverse to thelongitudinal axis of the spine) while minimizing vertical growth of theballoon. Such a balloon (which could simply be the previously describedembodiment when rotated 90° about its longitudinal axis) could be usedto initially create a cavity extending across substantially the entirevertebral body. After removal of the first balloon, a second balloon (ofthe same or different design) could subsequently be introduced into thehorizontal cavity and expanded. If desired, the second balloon couldsubstantially fill the horizontal cavity prior to inflation (therebymaximizing the surface area of the balloon facing the upper and lowerendplates) and, when expanded, could maximize the vertical forces whichultimately act on the endplates of the vertebral body (in an attempt todisplace the surrounding cortical bone).

[0192] If desired, a balloon chosen for treatment of a vertebral bodymay further incorporate restraints that cause the balloon to expand intoan irregular shape. In one embodiment disclosed herein, best shown inFIG. 23, the balloon desirably expands to a “peanut-like” shape whenviewed from the side. This embodiment will desirably create a cavitythat is similarly “peanut-shaped”, with the cavity essentiallycomprising a pair of enlarged cavity lobes that are separated by aregion of reduced cavity size—in other words, the cavity is dumb-bellshaped. Desirably, the filler material which occupies this cavity willharden, set and/or solidify into an implant having substantially theshape of the cavity into which it was introduced. By forming the implantinto this dumb-bell shape, the region of reduced width of the implantwill desirably help to anchor the implant within the cancellous bone,thereby reducing the opportunity for the implant to displace along thelongitudinal axis of the implant and/or migrate within or outside thetreated bone.

[0193] Furthermore, if desired a balloon used for treatment of avertebral body could incorporate additional restraints that alter theouter shape of the expanded balloon to further reduce the opportunityand/or tendency of an implant to migrate within and/or outside of atreated bone. For example, in one embodiment described above, theballoon incorporates an internal membrane which desirably causes theexpanded balloon to assume an indented or elongated “figure-8” shape incross-section (see FIG. 24c). This shape, if formed into the cavitywalls and ultimately assumed by the filler material, will desirablycreate an implant of similar cross-section. By forming the implant intothis figure-8 shape, the implant will desirably be anchored within thecancellous bone, thereby reducing the opportunity for the implant torotate about the longitudinal axis of the implant and/or migrate withinor outside the treated bone.

[0194] In addition to creating a desired shape and size to the cavity,which will desirably act as a mold to bound and shape the fillermaterial, the physician can further customize the shape of the implantin various ways. For example, after the initial cavity formation, butprior to the introduction of the filler material, the physician coulduse other surgical instruments to alter the shape and/or size of thecavity, such as by removing additional cancellous bone and/or scoringthe compressed cancellous bone along the walls—of the cavity. Similarly,prior to introducing the filler material the physician could introduceone or more additional balloons into the cavity to alter the existingcavity dimensions and/or create additional cavities of unique and/ordesired shape. The physician could alternatively choose to introduce twoor more different bone filler materials into a single cavity, withdifferent materials occupying different portions of the cavity and/orbeing intertwined, mixed or separated in some manner, if desired. Inaddition, after the filler material has filled the entire cavity, thephysician could continue introducing an additional amount of bone fillermaterial, which would desirably cause small amounts of the bone fillermaterial to interdigitate or flow into various gaps and/or cracks in thewalls of the cavity, thereby further anchoring the resulting implantwithin the cancellous bone. For example, the injection of an additional½ cc, 1 cc or 1½ cc of bone filler material (beyond the volume of thecavity created within the cancellous bone) can significantly increasethe interdigitation of bone filler material with the surroundingcancellous bone matrix.

[0195] IV. Other Uses, Methods and Balloons

[0196] The cavity created by the balloon can be filled with amedically-appropriate formulation of a drug or a growth factor. As anexample of delivering a drug, a typical dose of the antibiotic,gentamicin, to treat a local osteomyelitis (bone infection), is 1 gram(although the therapeutic range for gentamicin can be far greater, from1 nanogram to 100 grams, depending on the condition being treated andthe size of the area to be covered). A medically-suitable gel formulatedwith appropriate gel materials, such a polyethylene glycol, can contain1 gram of gentamicin in a set volume of gel, such as 10 cc. A balloonwith this volume whose shape and size is appropriate for the site beingtreated (that is, the balloon desirably will not break the cortical bonewhen inflated at the chosen site) can be used to compact the infectedcancellous bone. This creates a space that can be filled with theantibiotic gel in an open or minimally invasive procedure. This placesand holds the required amount of drug right at the site needingtreatment, and protects the drug from being quickly washed away by bloodor other fluids. Not only can the dose be optimized, but additionaldoses can be applied at later times without open surgery, enhancing thetherapeutic outcome. If the required cavity for the optimal drug doseweakens the bone, the bone can be protected from future fractures with acast or with current internal or external metal or plastic fixationdevices. The therapeutic substance put into bone may be acting outsidethe bone as well. A formulation containing chemotherapeutic agent couldbe used to treat local solid osteosarcoma or other tumor near that bone.

[0197] As an alternative, to deliver therapeutic substances, balloonscan be dipped in a medical formulation (often a dry powder, liquid orgel) containing a medically-effective amount of any desired antibiotic,bone growth factor or other therapeutic agent to coat the balloon withthe above-mentioned substance before it is inserted into a bone beingtreated. Optionally, the balloon can be wholly or partially inflatedwith air or liquid before the coating is performed. Optionally, thecoated balloon can be dried with air or by other means when the appliedformulation is wet, such as a liquid or a gel. The balloon is refoldedas required and either used immediately or stored, if appropriate anddesired. Coated on the balloon, therapeutic substances can be deliveredwhile cancellous bone is being compressed, or with an additional balloononce the cavity is made.

[0198] The methods described above can also be used to coat Gelfoam®absorbable gelatin powder or other agents onto the balloon before use.Such agents may also comprise substances that desirably promotecoagulation and/or thickening of body fluids. Inflating a Gelfoam-coatedballoon inside bone may further fill any cracks in fractured bone notalready filled by the compressed cancellous bone.

[0199] FIGS. 22A-C schematically illustrate one system and method fordelivering a therapeutic substance to the bone according to the presentinvention. As shown in FIG. 22A, an inflated balloon 229 attached to aninflating tube 230 is stabilized with a clip 231 that couples tube 230to a wire 232. As shown in FIG. 22B, a measured amount of gelformulation containing the desired amount of substance 233 is uniformlydispensed from a container 234, preferably in thin lines 235, onto theouter surface of a balloon 236. As shown in FIG. 22C, the coated balloon23 is then deflated and allowed to dry until the gel sets. The coatedballoon 237 is then ready for packaging for use by the surgeon. Ofcourse, the balloon can also be coated without prior inflation. Inaddition, the coating substance can be the desired compound alone in itsnatural state (solid, liquid or gas) or in an appropriate formulation,including a dry powder, an aerosol or a solution. The optional dryingtime will, of course, depend on the nature of the compound and itsformulation.

[0200] Delivering a therapeutic substance on the outside of the balloonused to compact the bone or with a second (possibly slightly larger)balloon after the bone is compacted, is qualitatively different thanputting formulated drug into the cavity. When delivered whilecompressing the bone, the substance becomes incorporated into thecompacted bone. This can serve as a way to instantly formulate a slowrelease version of the substance. It simultaneously allows the surgeonto fill the cavity with an appropriate supporting material, like acrylicbone cement or biocompatible bone substitute, so no casting or metalfixation is required. Such a combination allows the surgeon, forexample, to percutaneously fix an osteoporotic fracture while deliveringa desired therapeutic substance (like an antibiotic, bone growth factoror osteoporosis drug) to the site. Thus, casts or metal fixation devicesmay not be required in such instances.

[0201] Medically-effective amounts of therapeutic substances aretypically defined by their manufacturers or sponsors and are generallyin the range of 10 nanograms to 50 milligrams per site, although more orless may be required in a specific case. Typical antibiotics includegentamicin and tobramycin. Typical bone growth factors are members ofthe bone morphogenetic factor, osteogenic protein, fibroblast growthfactor, insulin-like growth factor, and transforming growth factor alphaand beta families. Chemotherapeutic and related agents include compoundssuch as cisplatin, doxorubicin, daunorubicin, methotrexate, taxol andtamoxifen. Osteoporosis drugs include estrogen, calcitonin,diphosphonates, and parathyroid hormone antagonists.

[0202] The balloons described in this invention can be used in opensurgical procedures at the sites discussed above to provide an improvedspace for inserting orthopedic implants, bone graft, bone substitutes,bone fillers or therapeutic substances. The size and shape of balloonchosen will be determined depending upon the site being treated as wellas the size, shape or amount of material that the surgeon wants toinsert into the remaining bone. Square and rectangular balloons can beused at any site for the placement of bone substitutes likehydroxyapatites which are available in those shapes. Balloons woulddesirably be made to match those predetermined sizes, and the surgeonwould chose the balloon to fit the size of material chosen.

[0203] To insert materials which do not flow into the balloon-madecavity, like hydroxyapatite granules or bone mineral matrix, the surgeoncan push them down a tube with a long pin whose diameter is slightlymore narrow than the inner diameter of the cannula through procedures inwhich the minimally-invasive procedure is taking place. During opensurgery, the surgeon can approach the bone to be treated as if theprocedure is percutaneous, except that here is no skin and other tissuesbetween the surgeon and the bone being treated. This desirably keeps thecortical bone as intact as possible. If the material to be inserted doesnot flow and should not be pushed into the cavity through a cannula (asin the case of the hydroxyapatite block, because that may result insignificant damage to the patient), the surgeon can make the cavityusing the “minimally invasive” approach, then punch a hole usingstandard tools (such as a punch, gouge or rasp) into one side of thecortical bone to allow insertion of the block. This same approach can beused for implanting a metal prosthesis, such as the metal tibialcomponent of a total knee replacement system.

[0204] Different sizes and/or shapes of balloons may be used at sitesnot specified above, such as the jaw bones, the midshaft of the arm andleg bones, the cervical vertebral bodies, the foot and ankle bones, theribs and the like. One of the keys to choosing balloon shape and size intreating or preventing bone fracture is the teaching of this applicationthat, optimally, up to 70-90% (or greater) of the cancellous bone can becompacted in cases where the bone disease causing fracture (or the riskof fracture) is the loss of cancellous bone mass (as in osteoporosis).Compacting less than 70-90% of the cancellous bone at the site beingtreated could possibly leave an extensive amount of the diseasedcancellous bone at the treated site. The diseased cancellous bone couldremain weak and later collapse, causing fracture despite treatment. Withthis principle, the allowed shapes and minimum sizes for any chosen boneare explained and defined.

[0205] Of course, there are many exceptions to this 70-90% cavity size,as generally described in this specification. One exception is when thebone disease being treated is localized, as in avascular necrosis, wherelocal loss of blood supply is killing bone in a limited area. In thatcase, the balloons can be smaller, because the disease area requiringtreatment is often smaller. A second exception is in the use of thedevices to improve insertion of solid materials in defined shapes, likehydroxyapatite and components in total joint replacement. In thesecases, the balloon shape and size is generally defined by the shape andsize of the material being inserted. Another exception is the deliveryof therapeutic substances. In this case, the cancellous bone may or maynot be affected. If it is not, some of the cancellous bone can besacrificed by compacting it to improve the delivery of a drug or growthfactor which has an important therapeutic purpose. In this case, thebone with the drug inside is supported while the drug works and then thebone heals through casting or current fixation devices. Anotherexception can involve the treatment of bone tumors, where the creationof a small cavity in cancellous bone adjacent the tumor could facilitatethe minimally invasive manipulation and/or removal of the tumor. Anotherexception could be where the quality of the cancellous bone is generallygood, but the bone has fractured and/or collapsed in some manner. Insuch a case, the creation of a small cavity within the strongercancellous bone may displace the cortical bone fragments to a positionat or near the fragments' normal anatomic positions withoutsignificantly compressing the cancellous bone.

[0206] Another key to choosing balloon shape and size is one teaching ofthis invention—that inelastic, elastic and/or semi-elastic balloonrestraints can be utilized and that inelastic or semi-elastic balloonmaterials are often preferred. Such materials can safely and easilyprevent the balloon from expanding beyond its predetermined shape andsize which can be defined by the limits of the normal dimensions of theoutside edge of the cancellous bone (which is inside of the corticalbone). A balloon which expands too much, for example, can create therisk of immediate fracture, so in one embodiment this defines the upperlimits of balloon sizes at each site. With many typical angioplastyballoons, surgeons usually rely on monitoring pressure (instead of theballoon design features of this invention) to prevent their balloonsfrom inflating too much. This often requires greater surgical skill thanthe teachings of the present application, which are to take an X-ray ofthe site to be treated and measure the important dimensions as describedherein. In addition, in bone treatment, relying on pressure can oftenresult in an inferior clinical outcome. The surgeon generally will notknow in advance what pressure is required to completely compact thecancellous bone, because this varies depending on the thickness of thecancellous bone and the extent to which it has lost density due to itsdisease. The surgeon is often likely to under inflate the balloon toavoid the potential consequences of overinflation and/or cortical bonefracture.

[0207] Another teaching of this application is that, while maximalpressures equally exerted in all directions can typically compress theweakest areas of cancellous bone, the use of restraints in a balloonbody will desirably control balloon expansion to some degree. If theballoon design does not incorporate restraints, it may not compresscancellous bone in an optimal manner for reinforcement and/or repair ofa fractured vertebral. The shape of the cancellous bone to becompressed, and the local structures that could be harmed if bone weremoved inappropriately, are generally understood by medical professionalsusing textbooks of human skeletal anatomy along with their knowledge ofthe site and its disease or injury. Ranges of shapes and dimensions aredefined by the site to be treated. Precise dimensions for a givenpatient can be determined by X-ray of the site to be treated, thetherapeutic goal and safety constraints at the site. For diseased bone,replacement of most of the cancellous bone may be desired, so a balloonwhose shape and size will compress around 70-90% (or greater) of thevolume of the cancellous bone in the treated region can be chosen.However, as previously noted balloons that are smaller or larger may beappropriate, particularly where localized bone treatments and/ordelivery of a therapeutic substance is the main goal. If desired, theballoon size can be chosen by the desired amount of therapeuticsubstance, keeping in mind that the balloon should desirably notdisplace the cortical bone beyond its normal unfractured dimensions.

[0208] While the new devices and methods have been more specificallydescribed in the context of the treatment of human vertebrae, it shouldbe understood that other human or animal bone types can be treated inthe same or equivalent fashion. By way of example, and not bylimitation, the present systems and methods could be used in any bonehaving bone marrow therein, including the radius, the humerus, thevertebrae, the femur, the tibia or the calcaneus. In addition, otherembodiments and uses of the invention will be apparent to those skilledin the art from consideration of the specification and practice of theinvention disclosed herein. All documents referenced herein arespecifically and entirely incorporated by reference. The specificationand examples should be considered exemplary only with the true scope andspirit of the invention indicated by the following claims. As will beeasily understood by those of ordinary skill in the art, variations andmodifications of each of the disclosed embodiments can be easily madewithin the scope of this invention as defined by the following claims.

We claim:
 1. A device capable of compressing cancellous bone comprisingan expandable body including an internal restraint coupled to the bodywhich directs expansion of the body, wherein the internal restraintincludes an internal membrane.
 2. A device according to claim 1 whereinthe expandable body includes an elongated axis, and wherein the internalrestraint includes an internal membrane that extends transversely of theelongated axis between opposing interior side surfaces of the expandablestructure.
 3. A device according to claim 1 wherein the expandable bodyincludes an elongated axis, and wherein the internal restraintincludes/n internal membrane that extends along the elongated axisbetween opposing end surfaces of the expandable structure.
 4. A deviceaccording to claim 1 wherein the expandable body includes an elongatedaxis, and wherein the internal restraint includes an internal membranethat extends in one direction along the elongated axis between opposingend surfaces of the expandable structure and in a second directiontransversely of the elongated axis between opposing interior sidesurfaces of the expandable structure.
 5. A device capable of compressingcancellous bone comprising an expandable body including an internalrestraint coupled to the body which directs expansion of the body,wherein the internal restraint directs expansion of the expandable bodymore in one direction than in another direction transverse the onedirection.
 6. A device capable of compressing cancellous bone comprisingan expandable body including an internal restraint coupled to the bodywhich directs expansion of the body, wherein the expandable bodyincludes an elongated axis, and wherein the internal restraintconstrains expansion of the expandable body along the elongated axis. 7.A device capable of compressing cancellous bone comprising an expandablebody including an internal restraint coupled to the body which directsexpansion of the body, wherein the expandable body includes an elongatedaxis, and wherein the internal restraint directs expansion of theexpandable body more in one radial direction from the elongated axisthan in a second radial direction from the elongated axis.
 8. A methodfor treating bone comprising the steps of inserting an expandable bodyinside bone, the expandable body including an internal restraint coupledto the body which directs expansion of the body, causing directedexpansion of the body in cancellous bone, and compacting cancellous boneby the directed expansion.
 9. A method according to claim 8 wherein thedirected expansion moves vertebral end plates.
 10. A method according toclaim 8 wherein the directed expansion lifts tibial plateau depressions.11. A method according to claim 8 wherein the directed expansion liftsproximal humerus depressions.
 12. A method according to claim 8 whereinthe directed expansion moves cortical bone.
 13. A method according toclaim 12 wherein the movement of cortical bone reduces a fracture.
 14. Amethod according to claim 8 wherein the step of compacting forms acavity.
 15. A method according to claim 14 further including the step offilling the cavity with a material.
 16. A method according to claim 15wherein the material comprises a biocompatible bone substitute.
 17. Amethod according to claim 15 wherein the material comprises bone cement.18. A method according to claim 15 wherein the material comprisessynthetic bone substitute.
 19. A method according to claim 15 whereinthe material comprises a flowable material that sets to a hardenedcondition.
 20. A device for compacting cancellous bone comprising a bodyadapted to be inserted into bone and undergo expansion in cancellousbone to compact cancellous bone, the body including material that,during the expansion in cancellous bone, applies a force capable ofmoving fractured cortical bone, and further includes an interiormembrane to constrain the expansion in cancellous bone.
 21. A deviceaccording to claim 20 wherein the expandable body includes an elongatedaxis, and wherein the internal membrane extends transversely of theelongated axis between opposing interior side surfaces of the expandablestructure.
 22. A device according to claim 20 wherein the expandablebody includes an elongated axis, and wherein the internal membraneextends along the elongated axis between opposing end surfaces of theexpandable structure.
 23. A device according to claim 20 wherein theexpandable body includes an elongated axis, and wherein the internalmembrane extends in one direction along the elongated axis betweenopposing end surfaces of the expandable structure and in a seconddirection transversely of the elongated axis between opposing interiorside surfaces of the expandable structure.
 24. A device according toclaim 20 wherein the internal membrane constrains expansion of theexpandable body more in one direction than in another directiontransverse the one direction.
 25. A device according to claim 20 whereinthe expandable body includes an elongated axis, wherein the internalmembrane constrains expansion of the expandable body along the elongatedaxis.
 26. A device according to claim 20 wherein the expandable bodyincludes an elongated axis, wherein the internal membrane constrainsexpansion of the expandable body more in one radial direction from theelongated axis than in a second radial direction from the elongatedaxis.
 27. A device according to claim 26 wherein the internal membraneconstrains-expansion of the expandable body along the elongated axis.28. A method for treating bone comprising the steps of inserting adevice as defined in claim 20 inside bone, causing constrained expansionof the body in cancellous bone, and compacting cancellous bone by theconstrained expansion.
 29. A method according to claim 28 wherein theconstrained expansion moves vertebral end plates.
 30. A method accordingto claim 28 wherein the constrained expansion lifts tibial plateaudepressions.
 31. A method according to claim 28 wherein the constrainedexpansion lifts proximal humerus depressions.
 32. A method according toclaim 28 wherein the constrained expansion moves cortical bone.
 33. Amethod according to claim 32 wherein the movement of cortical bonereduces a fracture.
 34. A method according to claim 28 wherein the stepof compacting forms a cavity.
 35. A method according to claim 34 furtherincluding the step of filling the cavity with a material.
 36. A methodaccording to claim 35 wherein the material comprises a biocompatiblebone substitute.
 37. A method according to claim 35 wherein the materialcomprises bone cement.
 38. A method according to claim 35 wherein thematerial comprises synthetic bone substitute.
 39. A method according toclaim 35 wherein the material comprises a flowable material that sets toa hardened condition.